Shanahan said the injury is a Grade 1 sprain of the lateral collateral ligament on the outside of the knee, caused when the rookie quarterback was hit at the end of a scramble late in regulation in the Redskins‘ 31-28 overtime win Sunday over the Baltimore Ravens.

Shanahan says Griffin has mild swelling and is receiving treatment multiple times a day.

“He’s definitely not ruled out for the Cleveland game,” Shanahan said.

The LCL is one of four ligaments in the knee. A Grade 1 sprain typically means the ligament is stretched or has some minor tears.

The most severe knee injury usually associated with sports is a season-ending torn ACL, the anterior cruciate ligament. Griffin tore the ACL in his right knee while playing for Baylor in 2009, but Shanahan said Griffin’s reconstructed ACL “looks great” and that there’s “no problem there.”

Fellow rookie Kirk Cousins will start if Griffin can’t. Cousins threw a touchdown pass with 29 seconds remaining in the fourth quarter and ran in the game-tying 2-point conversion after Griffin was hurt.

“Both of them will have a game plan,” Shanahan said. “And obviously Robert can do some things in the running game that Kirk can’t.”

The Redskins (7-6) have won four straight and trail the New York Giants by one game in the NFC East.